Hair straightener



FIG. 1 is a front, top and right side perspective view of a hair straightener showing my new design;

FIG. 2 is a front elevational view thereof:

FIG. 3 is a back elevational view thereof;

FIG. 4 is a left side elevational view thereof;

FIG. 5 is a right side elevational view thereof;

FIG. 6 is a top plan view thereof; and,

FIG. 7 is a bottom plan view thereof.

The dashed or broken lines shown in the drawings depict portions of the hair straightener in which the design is embodied that form no part of the claimed design. 

CLAIM The ornamental design for a hair straightener, as shown and described. 